Primer for improving the bonding of adhesives to nonporous substrates

ABSTRACT

A primer for promoting adhesion between an elastomeric adhesive and a nonporous substrate containing a silane-modified saturated polyester polymer and an adhesion promoter in an anhydrous solvent. The invention is also directed to a silane-modified saturated polyester polymer, and an adhesion promoter made by the reaction of a multifunctional isocyanate and an organosilane.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. patent application Ser. No.09/107,810, filed Jun. 30, 1998 now U.S. Pat. No. 6,008,305.

FIELD OF THE INVENTION

The invention relates to primer compositions for improving the bondingof elastomeric adhesives, such as urethanes, silylated urethanes,silyl-terminated polyethers and silicones to nonporous substrates, suchas coated and uncoated metal, glass and polymeric surfaces. Moreparticularly, the invention relates to such primer compositions, methodsfor making such compositions, and methods for their use.

BACKGROUND OF THE INVENTION

In the manufacture of motor vehicles, glass components, such aswindshields, side windows and backlights, are joined to the metalvehicle body by means of an elastomeric adhesive material which may alsofunction as a sealant. The adhesive materials which are used for thispurpose are required to meet a number of criteria including appearance,ease of application, shear strength, and adhesion in crash tests.Therefore, good adhesion is required between the adhesives and thevarious nonporous metal, glass and polymeric substrates to which it isbonded.

In order to obtain acceptable levels of adhesion between the adhesivesand the nonporous surfaces, various primers have been used to precoatthe nonporous surfaces to enable the adhesive to bond better to them. Inoriginal equipment manufacture and glass replacement processes, primersare generally applied to both the metal and glass surfaces prior toapplication of the adhesive. The metal surfaces may be aluminum orsteel, and may be bare, treated, or coated with various types of paintsor enamels. Various polymeric materials may also be used in place of theglass components, or as structural members in place of the metalcomponents. A current technique for joining glass to metal in vehiclesuses an elastomeric urethane or silylated urethane adhesive. Otherelastomeric adhesives which can be used include silyl-terminatedpolyethers and silicones. All of these adhesives may also be used tobond polymeric substrates to glass or metal, or to each other.

A number of primer compositions have been proposed for promotingadhesion between urethane adhesives or sealants and nonporous materialsin technologies relating to motor vehicle manufacture as well as otherareas.

For example, U.S. Pat. No. 3,707,521, and its divisional, U.S. Pat. No.3,779,794, discuss a polyurethane adhesive primer composition comprisinga branched polyurethane polymer in combination with a latent catalystfor the moisture curing of free isocyanate groups present.

U.S. Pat. No. 4,882,003 is directed to sealant primer compositionsuseful for promoting adhesion to enamel paint coated substrates, inwhich the primer comprises an acrylic polymer base composition, pigment,and a solvent effective to interpenetrate the enamel substrate coating.

U.S. Pat. No. 4,857,366 describes the use of a primer solution ofp-toluenesulfonic acid and an organofunctional. silane in solvent priorto applying an uncured urethane sealant to painted or glass surfaces.

U.S. Pat. No. 4,625,012, incorporated herein by reference for itsdiscussion of isocyanatosilane adducts, describes a method of making apolyurethane polymer by reacting an isocyanatosilane adduct having atleast two isocyanato groups with another isocyanate and a polyol.

U.S. Pat. No. 5,238,993 is directed to a primer comprising a solution ofa polyester resin derived from a carboxylic acid and a glycol, anisocyanate and a silane-containing moiety dissolved in a particularmixture of solvents.

Because of the different properties of the various coated and uncoatedmetal, glass and polymeric substrates, different primers have been usedon different types of substrates to obtain optimal adhesion with theadhesives. That is, each nonporous surface being bonded may require itsown specific type of primer. Furthermore, primers used with urethaneadhesives may not be acceptable for use with silylated urethane,silyl-terminated polyether or silicone adhesives. Therefore, a widevariety of primers have been needed to promote the bonding of differentadhesives to different glass, metal and polymeric substrates.

For original equipment manufacturers, it may be reasonable to select aspecific primer for a particular combination of adhesive and substrate,and to use different primers on the metal, glass and polymeric surfaces.However, for glass replacement operations working with a variety ofmetal, glass and polymeric substrates, as well as various adhesivematerials, it can be very difficult to maintain and use a wide varietyof different primers.

Thus, there is a need for a universal primer which can be used topromote adhesion between the various elastomeric adhesives and thedifferent nonporous substrates to which they must adhere. There is aparticular need for such a primer which can be used with the newersilylated urethanes and silyl-terminated polyethers as well as with theconventional urethane adhesives.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with the present invention, there is provided a primercomposition for improving the bonding of elastomeric adhesives tononporous surfaces. The primer provides quick initial adhesion andstrong ultimate adhesion. The primer may be used with a variety ofadhesives, including urethanes, silylated urethanes, silyl-terminatedpolyethers and silicones. The substrates to which the adhesive may bebonded include treated or untreated metal, glass and polymeric surfaces,with or without a coating, paint or primer. Such substrates include theglass materials used in motor vehicle components such as windshields,side windows and backlights, with or without ceramic frit on thesurface, as well as the body substrates to which they are adhered.

The primer of the present invention comprises:

a) from about 4 to about 20 weight percent of a silane-modifiedpolyester polymer;

b) from about 2 to about 14 weight percent of an adhesion promoter,preferably a silane-modified multifunctional isocyanate; and

c) from about 50 to about 90 weight percent of an anhydrous solvent forsaid silane-modified polymer and said adhesion promoter.

The polymer used in the primer is a silane-modified polyester, which ispreferably saturated and preferably linear. In addition to improvingadhesion, this polymer is believed to help the primer form a thin anduniform film on a substrate. Good results are obtained with a primercontaining from about 4 to about 20 weight percent (wt %) of thesilane-modified polymer, with all percentages by total weight of theprimer unless stated otherwise. Preferably, the primer contains fromabout 8 to about 14 wt % of this silane-modified polymer, and morepreferably from about 10 to about 12 wt %.

In one embodiment, the silane-modified polymer is of the formula:##STR1## wherein: R is a divalent organic moiety, preferably a C₁₋₆alkylene group, and more preferably propylene.

R¹ is hydrogen or a C₁₋₄ alkyl group, preferably hydrogen.

R² is a C₁₋₆ alkyl group, preferably methyl, ethyl or propyl, mostpreferably methyl.

The value of n is 0 or 1, but is preferably 0. That is, the Si group canhave one R¹ and two OR² substituents, but preferably just has three OR²substituents.

The ##STR2## represents a moiety of a difunctional polyester polyol ofgeneral formula ##STR3## which is preferably saturated, preferablylinear, and preferably of a molecular weight from about 20,000 to about30,000 Daltons.

This embodiment of the silane-modified polymer may be made by reacting:

a) a difunctional polyester polyol dissolved in an anhydrous solvent;with

b) an isocyanatosilane of the formula:

    O═C═N--RSiR.sup.1.sub.n (OR.sup.2).sub.3-n

wherein R, R¹, R² and n are as defined above.

A sufficient amount of the isocyanatosilane should be included to reactwith all of the active hydroxyl groups on the polyol. One reason forpreferring to react all of the hydroxyl groups is that the adhesionpromoter component of the primer includes active isocyanate groups whichcould undesirably react with any unreacted hydroxyl groups on thepolymer, especially in the presence of catalyst. Preferably, an excessof the isocyanatosilane is used in the process for forming thesilane-modified polymer to prevent such subsequent reaction with theadhesion promoter.

Polyester polyols are well-known polyester resins which are typicallyproducts of carboxylic acids and glycols. Preferably a saturatedpolyester polyol is used. In addition, preferably the polyester polyolis a linear polymer, and preferably it has a molecular weight of fromabout 20,000 to about 30,000 Daltons. The resin should also be one whichis soluble in an anhydrous solvent.

A particularly preferred linear saturated polyester polyol with amolecular weight of about 25,000 is sold under the tradename VITEL®2200B, and is commercially available from Bostik, Inc.

Examples of commercially available isocyanatosilanes which are suitablefor use in the above reaction includegamma-isocyanatopropyltrimethoxysilane, available as Silquest® Y-5187from OSi Specialties Group, a Witco company (OSi), andgamma-isocyanatopropyltriethoxysilane, available as Silquest® A-1310,also from OSi.

The solvent for this reaction process should be one which will not reactwith NCO groups. It should therefore be as anhydrous as reasonablypossible. Preferably, the solvent should also be able to dissolve the a)and b) reactants at temperatures as low as about 5° C. Examples ofsuitable solvents include methyl ethyl ketone (MEK), MEK/toluene blends,MEK/ethyl acetate blends, cyclic ethers, chlorinated solvents andmixtures thereof.

In another embodiment the silane-modified polymer is of the formula:##STR4## wherein the ##STR5## group, R, R¹, R² and n are as definedabove in regard to the polymer of Formula I.

X represents an ##STR6## group or an S, wherein each X may be the same,or different X groups can be combined.

R³ represents H, a C₁₋₆ organic moiety, or a second RSiR¹ _(n)(OR²)_(3-n) group, which may be the same as or different from the firstsuch group. Preferred organic moieties for use as R³ include linear orbranched C₁₋₆ alkyl and cyclohexyl groups, and, in a particularlypreferred embodiment, R³ is a phenyl group.

R⁴ represents a divalent organic moiety which preferably has a molecularweight of less than about 2000, more preferably less than about 1000,and most preferably less than about 200.

This embodiment of the silane-modified polymer may be made by firstreacting a difunctional saturated polyester polyol dissolved in ananhydrous solvent, as described above in regard to the polymer ofFormula I, with at least one difunctional isocyanate of the formulaOCN--R⁴ --NCO, to produce an isocyanate-terminated intermediate product.A stoichiometric two-to-one molar ratio of difunctional isocyanate topolyol is preferably used to ensure that each available hydroxyl groupon the polyol reacts with a difunctional isocyanate.

As discussed above, R⁴ represents a divalent organic moiety whichpreferably has a molecular weight of less than about 2000, morepreferably less than about 1000, and most preferably less than about200.

Diisocyanates suitable for use in this reaction are well known in theart. Among the suitable diisocyanates are aromatic monomericdiisocyanates such as 4,4'-diphenylmethane diisocyanate (MDI) andtoluene diisocyanate (TDI); aliphatic monomeric diisocyanates such ashexamethylenediisocyanate (HDI); 4,4-dicyclohexylmethane diisocyanate(hydrogenated MDI or HDMI); isophoronediisocyanate; and combinations andderivatives thereof.

The isocyanate-terminated intermediate product of the above reaction isthen reacted with at least one organosilane containing an NCO-reactinghydrogen. Preferably, at least a two-to-one molar ratio of organosilaneto intermediate product is used. Suitable organosilanes include amino-or mercapto-alkoxysilanes of formula: ##STR7## or of formula:

    HSRSiR.sup.1.sub.n (OR.sup.2).sub.3-n                      (IV)

or mixtures thereof,

wherein R, R¹, R², R³ and n are as defined above.

In one preferred embodiment of this silane-modified polymer of thepresent invention, the organosilane is an amino-alkoxysilane inaccordance with Formula III, and the R₃ group is a C₁₋₆ organic moiety.As discussed above, preferred organic moieties for use as R³ includelinear or branched C₁₋₆ alkyl and cyclohexyl groups, and, in aparticularly preferred embodiment, R³ is a phenyl group. A preferred,commercially available phenyl amino-alkoxysilane in accordance with thisembodiment is N-phenyl-gamma-aminopropyltrimethoxysilane, available asSilquest® Y-9669 from OSi.

Another commercially available amino-alkoxysilane isN,N-bis[(3-trimethoxysilyl)propyl]amine, available as Silquest® A-1170from OSi.

A preferred, commercially available mercapto-alkoxysilane in accordancewith Formula IV is gamma-mercaptopropyltrimethoxysilane, available underthe names Silquest® A-189 and Y-11167 from OSi Specialties Group, orunder the name DYNASYLAN® MTMO from Huls. Another preferredmercapto-alkoxysilane is gamma-mercaptopropylmethyldimethoxysilane,available as DYNASYLAN® 3403 from Huls.

The adhesion promoter of the present invention is preferably thereaction product of a multifunctional isocyanate, or a combination ofmultifunctional isocyanates, which should have at least three isocyanategroups per molecule, preferably trifunctional or quadrifunctionalisocyanates, with an organosilane. The multifunctional isocyanate isreacted with at least one organosilane containing at least oneNCO-reacting hydrogen in proportions to leave at least two unreactedisocyanate groups per molecule in the reaction product. Preferably onemole of the organosilane is reacted with one mole of the multifunctionalisocyanate.

Such an adhesion promoter improves the adhesion between a substrate andan adhesive because of its unique chemical structure with both NCO andsiloxane groups. Good results are obtained with a primer containing fromabout 2 wt % to about 14 wt % adhesion promoter. Preferably the primercontains at from about 6 to about 10 wt %, more preferably from about 7to about 9 wt % of the adhesion promoter.

A preferred multifunctional isocyanate suitable for use in the abovereaction is tris(4-isocyanatophenyl)thiophosphate, which is commerciallyavailable from Bayer as a 27 wt % solution in ethyl acetate which issold under the name Desmodur® RF-E. Other suitable commerciallyavailable multifunctional isocyanates includetris(4-isocyanatophenyl)methane, which is commercially available as a 27wt % solution in ethyl acetate under the name Desmodur® RE from Bayer;the reaction products of trimethylolpropane with 3 moles of adiisocyanate; diisocyanate trimers such as those identified as HDItrimer, and 2,4-TDI trimer or 2,6-TDI trimer; and isophoronediisocyanate trimer. Biurets, which are reaction products of urea andisocyanate may also be used, such as HDI biuret, commercially availableas Desmodur® N from Bayer. Various polymeric MDI materials may also beused.

The multifunctional isocyanate is reacted with an organosilanecontaining at least one NCO-reacting hydrogen. Suitable organosilanesfor use in this reaction include the amino- and mercapto-alkoxysilanesof Formulas III and IV as discussed above.

In one preferred embodiment of the adhesion promoter of the presentinvention, the organosilane is an amino-alkoxysilane in accordance withFormula III, and the R₃ group is a C₁₋₆ organic moiety. As discussedabove, preferred organic moieties for use as R³ include linear orbranched C₁₋₆ alkyl and cyclohexyl groups, and, in a particularlypreferred embodiment, R³ is a phenyl group. A preferred, commerciallyavailable N-phenylamino-alkoxysilane in accordance with this embodimentis N-phenyl-gamma-aminopropyltrimethoxysilane, available as Silquest®Y-9669 from OSi.

A preferred, commercially available mercapto-alkoxysilane in accordancewith Formula IV is gamma-mercaptopropyltrimethoxysilane available underthe names Silquest® A-189 and Y-11167 from OSi Specialties Group, orunder the name DYNASYLAN® MTMO from Huls. Another preferredmercapto-alkoxysilane is gamma-mercaptopropylmethyldimethoxysilane,available as DYNASYLAN® 3403 from Huls.

A multifunctional isocyanate of general formula A(NCO)_(n), would yieldthe following products of Formulas V or VI when reacted, respectively,with organosilanes of the above Formulas III or IV: ##STR8## wherein m'and n' are integers, and m' is less than n'. Preferably, n'-m' equals 1.That is, preferably only one of the available NCO groups on themultifunctional isocyanate reacts with the organosilane, leaving atleast two unreacted isocyanate groups per molecule.

The reaction is preferably carried out with the addition of heat and inthe presence of a suitable catalyst, as would be known by one skilled inthe art. Suitable catalysts may include those which could also be addedto the primer, as discussed below.

The primer of the present invention preferably comprises thesilane-modified polyester polymer of the present invention incombination with an adhesion promoter which is the reaction product of amultifunctional isocyanate and a silane. However, the silane-modifiedpolyester polymer of the present invention can also be used in primercompositions which do not contain the adhesion promoter of the presentinvention. For example, the silane-modified polyester polymer can beused to improve existing primer compositions, or to develop new primercompositions. In such cases, other adhesion promoters may be used. Inlike manner, the adhesion promoter of the present invention can be usedin primer compositions which do not contain the silane-modifiedpolyester polymer.

The solvent used in the primer of the present invention should becapable of dissolving the silane-modified polymer and the adhesionpromoter. It should also be anhydrous, because of the high reactivity ofNCO and siloxane groups with water. Likewise, the solvent itself shouldnot be reactive with the other components of the primer. In particular,the solvents should not contain any NCO-reacting hydrogens.

For reasonable evaporation rates and drying of the primer, the solventshould preferably have a flash point of less than 40° C. Suitablesolvents include acetone, methyl acetate, ethyl acetate and propylacetate. Higher boiling point solvents such as toluene, xylene or methylpropyl ketone may also be used. Different solvents can be combined toproduce a final solvent which has the desired evaporation rate, andresults in the formation of a uniform primer film on a substrate.

Enough solvent should be included in the primer to produce a thin anduniform film. The primer should comprise from about 50 to 90 wt %solvent, preferably from about 55 to about 85 wt %, and more preferablyfrom about 60 to about 80 wt %.

The primer of the present invention may also include a catalyst forpromoting 1) the reaction of isocyanate and siloxane groups withatmospheric moisture, 2) the condensation reaction of silanol groups,and 3) the reactions at the interfaces between the primer and thesubstrates and between the primer and the elastomeric adhesive. Examplesof suitable catalysts include tertiary amines, such as1,3,4-trimethylpiperazine; N,N'-dimorpholinodiethyl ether; organotincompounds, such as dibutyltin dilaurate and dibutyltin diacetate; andcombinations thereof. Particularly good results may be obtained using acombination of tertiary amine and organotin catalysts, because of anapparent synergism.

The same or different catalysts may also be used in the preparation ofthe silane-modified polymer and adhesion promoter components of theprimer. As a result, there may already be catalyst present in the primercomposition when these components are combined. Preferably, the primershould contain at least about 0.05 wt % of catalysts to promote theabove reactions, more preferably at least about 0.08 wt %, and even morepreferably at least about 0.1 wt %. However, the presence of too muchcatalyst can reduce the shelf life of the primer, and cause reactions tooccur too quickly. Preferably, the total amount of catalyst present inthe primer is less than about 0.8 wt %, more preferably less than about0.4 wt %, and even more preferably less than about 0.2 wt %.

The primer composition may also contain various additives which would bewell known to one skilled in the art. Such additives include, but arenot limited to, moisture scavengers, NCO stabilizers, fillers, includingcarbon black as well as non-black fillers, and defoaming agents.

To maintain the primer as anhydrous as possible by removing traces ofwater, one or more moisture scavengers may also be included in theprimer. Because of the high reactivity of NCO and siloxane groups withwater, moisture scavengers can be very important for reasonable shelflife and good performance of the primer. Enough scavenger should beincluded to take care of all the moisture. However, excess amounts ofscavengers can adversely affect the rheology and performance of theprimer. Preferably the primer contains from about 0.1 to about 1 wt % ofsuch scavengers, preferably from about 0.3 to about 0.7 wt %, withparticularly good results at a content of about 0.5 wt %. Well-knownmoisture scavengers which are suitable for use in the primers of thepresent invention include 3 Å (0.3 nm) pore molecular sieves, p-toluenesulfonyl isocyanate, silanes, such as vinyltrimethoxysilane andtetramethoxysilane, and combinations thereof.

To further improve shelf life, one or more NCO stabilizers may also beincluded in the primer. However, these should be added sparingly toavoid interfering with the adhesion performance of the primer.Therefore, the primer should contain not more than about 0.05 wt % NCOstabilizer, preferably about 0.001 to about 0.01 wt %, with good resultsat about 0.005 wt %. An example of an NCO stabilizer is benzoylchloride.

Various fillers may also be included in the primer composition. Carbonblack may be added as a pigment, UV absorber and reinforcing agent, andto modify the rheological properties of the primer, such as viscosity,sag resistance, and flow rate. It also creates channels for moisture toget into the primer film and vapor to escape during curing. When added,enough carbon black should be used to obtain the desired properties inthe primer film. However, an excess can cause rheological problems andloss of strength. The amount of carbon black used should be less thanabout 12 wt %, preferably less than about 8 wt %, and more preferablyless than about 6 wt %. Preferably, a minimum of about 3 wt % carbonblack is used, more preferably at least about 4 wt %.

Non-black fillers may also be used in addition to, or in place of thecarbon black filler. If a non-black primer is desired, then non-blackfillers can be used instead of carbon black. Such fillers can also beused, with or without carbon black, to adjust rheological properties,give soft settlement, reinforce the primer and create channels formoisture and vapor. The amount of these fillers used will depend onwhether it is used instead of carbon black, or in addition to carbonblack. In general, the primer should contain no more than about 20 wt %of the non-black fillers, and preferably less than about 6 wt %, morepreferably less than about 5 wt %. A minimum of about 2 wt % of suchfillers is preferably used, more preferably at least about 3 wt %, toobtain the desired effects on the primer.

The primer may also include one or more anhydrous defoaming agents tohelp form a smooth primer film. Such defoaming agents are well-known tothose skilled in the art. No more than about 1 wt % defoaming agentshould be used, to avoid undesirable affects on adhesion. Preferablyless than about 0.6 wt % is used, more preferably less than about 0.4 wt%. Preferably, a minimum of about 0.1 wt % is used for defoaming, morepreferably at least about 0.2 wt %.

The primer of the present invention may be used in a method forpromoting the adhesion of an elastomeric adhesive to one or morenonporous surfaces. Thus, the primer can be used to promote the bondingof one nonporous surface to another, when they are adhered to each otherby means of an elastomeric adhesive. The primer is applied to thenonporous surface or surfaces, and preferably allowed to set for atleast about 20 minutes prior to applying the elastomeric adhesive. Anadvantage of the present invention is that the same primer can beapplied to different nonporous surfaces which are being bonded to eachother by means of an elastomeric adhesive, and may also be used withdifferent elastomeric adhesives.

The nonporous surfaces may include structural substrates such as treatedor untreated metal surfaces, with or without a coating, paint or primer,glass substrates such as motor vehicle windshields, side windows andbacklights, with or without ceramic frit or other coatings on thesurface, and polymeric substrates which may be used as either structuralor light-passing components. Metal substrates include essentially allmetals, such as, without limitation, the steel and aluminum used forwindow frames in motor vehicles and buildings. The metal may or may notbe treated, as by galvanizing or anodizing, or may or may not be coatedwith a paint, enamel or other primer. The glass substrate may beuncoated window glass, or may be coated with ceramic frit, tinting,polymeric material, or any other glass adherent coating.

The primer of the present invention may be used with a wide variety ofpolymeric substrates. For example, good results were obtained using thepresent primer on polyvinyl chloride, polyurethane, polycarbonate andpolyvinyl acetate surfaces.

EXAMPLE 1 Preparation of Silane-Modified Polymer

A silane-modified polymer of the type set forth in Formula I above ismade in accordance with the present invention by the reaction of alinear saturated polyester polyol with an isocyanatosilane. 87.00 gVITEL® 2200B polyester polyol (MW 25,000 Daltons, sold by Bostik, Inc.)is dissolved in 210.80 of methyl ethyl ketone (MEK). Then, 3.01 g ofgamma-isocyanatopropyltrimethoxysilane (Silquest® Y-5187 sold by OSiSpecialties Group) is added to react with the polyester polyol in thepresence of 0.0103 g of dibutyltin diacetate (METACURE® T-1 from AirProducts and Chemicals, Inc.) at 70° C. for about 3 hours underanhydrous conditions. Analysis indicated that essentially all of theavailable OH groups of the polyester polyol had reacted with the silane.

EXAMPLE 2 Preparation of Adhesion Promoter

An adhesion promoter is made in accordance with the present invention byreacting an equimolar mixture of multifunctional isocyanate with anorganosilane containing an NCO-reacting hydrogen. 175.48 g of Desmodur®RF-E (27% by weight of tris(4-isocyanatophenyl)thiophosphate in ethylacetate, sold by Bayer) reacts with 21.79 g of A-189™(gamma-mercaptopropyltrimethoxysilane from OSi) in the presence of0.0190 g of dibutyltin diacetate at 73° C. for about 2 hours underanhydrous conditions. Analysis indicated that, as desired, approximatelyone-third of the available NCO groups reacted with the NCO-reactinghydrogens of the organosilane.

EXAMPLE 3 Preparation of Primer

A primer is prepared in accordance with the present invention using thesilane-modified polymer of Example 1 and the adhesion promoter ofExample 2. The components are combined in a suitable mill, such as aball mill or a shot mill. 9.99 g of dried Sterling® R carbon black (soldby Cabot Corp.), 6.00 g of dried Monomix™ talc (sold by Luzenac America,Inc.), 38.03 g of anhydrous ethyl acetate, 28.10 g of anhydrous MEK,0.0600 g of METACURE® T-1 dibutyltin diacetate, 0.0796 g of1,2,4-trimethylpiperazine, 0.40 g of BYK®-070 defoaming agent (sold byBYK-Chemie USA) and 0.50 g of Baylith® L Powder (3 Å (0.3 nm) molecularsieves sold by Bayer) are charged into the mill and milled until theparticle size reaches about 7 Hegman on a Hegman gauge (12.5 μm). Then,69.90 g of a silane-modified polymer prepared in accordance with Example1, 46.02 g of adhesion promoter prepared in accordance with Example 2,and 0.0100 g of benzoyl chloride are added into the mill and milled forone hour. The resulting primer is stored in small containers filled withnitrogen in the head space.

EXAMPLE 4 Peel Adhesion Tests

The primer of Example 3 was tested for its ability to promote bondingbetween several elastomeric adhesives and various nonporous substrates.The primer is applied to the coupon to a nominal thickness of 20 to 40μm, and allowed to air dry for at least 20 minutes at 23° C. and 50%relative humidity. Beads of adhesive (about 3 mm thick, 15 mm wide) areapplied to the primered substrate, and cured at 23° C. and 50% relativehumidity for about 16 hours. The adhesive beads are then cut with ablade through the primer layer, and an attempt is made to peel the beadsfrom the substrates by pulling.

The failure mode for each test specimen is recorded. There are threetypes of failure modes, cohesive failure, adhesive failure, and acombination of both. Cohesive failure is one in which the adhesiveadheres strongly to the primered substrate, and the failure occurs bybreaking the adhesive. Adhesive failure is one in which the adhesiveseparates from the substrate, with the failure at the interface betweenthe primer and the substrate or between the primer and the adhesive.Preferred primers are ones for which the failure mode is a 100% cohesivefailure, indicating a strong bond between the primer and both thesubstrate and the adhesive.

Tests were conducted using five different commercially availableelastomeric adhesives. The first four were ADCO FC-1000™ fast curingsilylated urethane auto glass adhesive, ADCO FC-2000™ high viscositysilylated urethane auto glass adhesive, ADCQ AD-380™ quick curingurethane glass adhesive, and TREMSHIELD® 660 heavy body urethaneadhesive (all available from ADCO Products, Inc., an AlliedSignalcompany). The fifth adhesive was U-400™ urethane adhesive, availablefrom Essex Specialty Products, Inc.

The glass substrates tested were glass and ceramic fritted glass. Themetal substrates tested were aluminum, cold rolled steel, galvanizedsteel, E-coated steel, enamel topcoated steel (using JEN IV™ enamel fromDuPont, and DCT-5000™ coating from PPG), and steel with an old urethaneprimer coating (primers tested were WIP-40™, a pinchweld primer fromADCO, and U-413™, a pinchweld primer from Essex). The polymer substratestested were polyvinylchloride, polyurethane, polycarbonate and polyvinylacetate.

All of the different elastomeric adhesives were tested with all of thelisted substrates. In all of the tests, the failure mode for the Example3 primer of the present invention was 100% cohesive failure. The resultsdemonstrate that the primer of the present invention is suitable for useon a wide range of substrates with a wide range of different elastomericadhesives.

EXAMPLE 5 Lap Shear Strength Tests

Tests were conducted in accordance with the standard General Motors testset forth in "Shear Adhesion Test for Adhesives Used in Glass BondingProcedure" (GM9521P, General Motors Engineering Standards, January1992), incorporated herein by reference. The crosshead speed was 50mm/minute, rather than the GM standard of 130 mm/minute. The lap shearstrength was measured during the curing process for bonding samples ofmetal with an existing layer of U-400 adhesive to ceramic fritted glassprimed with the primer of Example 3, using ADCO FC-1000™ and ADCOFC-2000™ adhesives. After three hours of curing, all of the samples haddeveloped a lap shear strength in excess of 1000 kPa. After five hoursof curing, the FC-1000 samples had developed a lap shear strength ofabout 1700 kPa, while the FC-2000 sample was at over 2300 kPa. Acomparison test was conducted using the FC-1000 adhesive and acommercially available glass primer (ADCO GP-60™ glass primer, precededby cleaning with ADCO CF-20™ cleaner). After three hours, the lap shearstrength was about 150 kPa, and after five hours, it was up to about1000 kPa. These results demonstrate the quick adhesion development ofthe primer of the present invention.

EXAMPLE 6 Automobile Crash Test

When primers are used to bond windshields to automobile bodies, they maybe subjected to actual vehicle crash tests. The purpose of this test isto determine whether the primer and adhesive are capable of retainingthe windshield attached to the car body in a simulated frontal crash.The present test was conducted after a relatively short time period offour hours after the windshield was replaced using the bonding system ofADCO FC-1000™ adhesive and the primer of Example 3. The test wasconducted using NHTSA's Office of Vehicle Safety Compliance (OVSC)Laboratory Test Procedure No. TP-301-01 as a guideline. A 1996 FordTaurus® car was used as the test vehicle. The original windshield wasremoved and a new replacement windshield installed using ADCO FC-1000™adhesive. Before applying the adhesive, the primer of Example 3 wasapplied to both the new windshield and the body-side substrate, whichstill had some existing primer and adhesive present. The primer wasallowed to set for about 20 minutes. The adhesive and primer wereallowed to cure for four hours, with the temperature ranging from 68 to73° F. (20-23° C.), and the relative humidity from 46% to 53%,respectively. The vehicle was equipped with air bags, and uninstrumenteddummies restrained with seatbelts were in the front seats. The vehiclewas traveling at about 35 mph when it impacted a flat frontal barrier.The windshield shattered, but retention of the windshield by the bodysubstrate was 100%.

This results indicate this bonding system passed this test and wouldtherefore be qualified for use in windshield installations. It issignificant to note that this bonding system was able to pass the testafter only four hours of curing. This provides a relatively short timefor safely driving away after a windshield replacement.

EXAMPLE 7

Another silane-modified polymer of the type set forth in Formula I ismade by the process set forth in Example I, except thatgamma-isocyanatopropyltriethoxysilane, available from OSi as Silquest®A-1310, is used as the isocyanatosilane. In this case, with reference toFormula I, R² is an ethyl group, instead of a methyl group which wouldbe the case for Example 1. The silane-modified polymer of this examplecan also be used to produce primers in accordance with the presentinvention.

EXAMPLE 8

This example illustrates the preparation of a silane-modified polymer ofthe type set forth in Formula II above. In this process, one mole of thesame polyester polyol used in Example 1 is first reacted with two molesof a difunctional isocyanate. The difunctional isocyanates used arecommercially available MDI, TDI, HDMI and HDI, as identified above. Ineach case, the isocyanate is reacted with the polyol to form anisocyanate terminated intermediate product.

The intermediate products are each then reacted further with two molesof various organosilanes to form silane-modified polymers of the typeset forth in Formula II. A first set of samples is made by combiningeach of the intermediate products with an amino-alkoxysilane inaccordance with the above Formula III. The silane used for these samplesis N-phenyl-gamma-aminopropyltrimethoxysilane, available as Silquest®Y-9669 from OSi. A second set of samples is made by combining each ofthe intermediate products with a mercapto-alkoxysilane in accordancewith Formula IV. The silanes used for these samples aregamma-mercaptopropyltrimethoxysilane, available as Silquest® A-189 fromOSi, and gamma-mercaptopropylmethyldimethoxysilane, available asDYNASYLAN® 3403 from Huls. Each of the silane-modified polymers of thisexample can then be used to produce primers in accordance with thepresent invention.

EXAMPLE 9

In this example, other samples of silane-modified multifunctionalisocyanate adhesion promoters are made in accordance with the processset forth in Example 2. In each case an equimolar mixture of amultifunctional isocyanate is reacted with an organosilane in accordancewith Formula III or IV above, each containing an NCO-reacting hydrogen.The multifunctional isocyanates used aretris(4-isocyanatophenyl)methane, available as a 27 wt % solution inethyl acetate under the name Desmodur® RE from Bayer; commerciallyavailable diisocyanate trimers including HDI trimer, 2,4-TDI trimer and2,6-TDI trimer; isophorone diisocyanate trimer; and HDI biuret,commercially available as Desmodur® N from Bayer.

A first set of samples is made by combining each of the multifunctionalisocyanates with an amino-alkoxysilane in accordance with the aboveFormula III. The silane used for these samples isN-phenyl-gamma-aminopropyltrimethoxysilane, available as Silquest®Y-9669 from OSi. A second set of samples is made by combining each ofthe multifunctional isocyanates with a mercapto-alkoxysilane inaccordance with Formula IV. The silanes used for these samples aregamma-mercaptopropyltrimethoxysilane, available as Silquest® A-189 fromOSi, whcih was used in Example II, andgamma-mercaptopropylmethyldimethoxysilane, available as DYNASYLAN® 3403from Huls. Each of the silane-modified adhesion promoters of thisexample can then be used to produce primers in accordance with thepresent invention.

Having thus described a few particular embodiments of the invention,various alterations, modifications, and improvements will readily occurto those skilled in the art. Such alterations, modifications andimprovements as are made obvious by this disclosure are intended to bepart of this description though not expressly stated herein, and areintended to be within the spirit and scope of the invention. Theforegoing description is by way of example only, and not limiting. Theinvention is limited only as defined in the following claims andequivalents thereto.

We claim:
 1. A primer comprising:a) from about 4 to about 20 weightpercent of a silane-modified polyester polymer; b) from about 2 to about14 weight percent of an adhesion promoter; and c) from about 50 to about90 weight percent of an anhydrous solvent.
 2. The primer of claim 1wherein the silane-modified polyester polymer has the formula: ##STR9##wherein: the ##STR10## represents a moiety of a difunctional polyesterpolyol of general formula ##STR11## X represents an ##STR12## group oran S, and each X may be the same or different; each R represents adivalent organic moiety;each R¹ represents hydrogen or a C₁₋₄ alkylgroup; each R² represents a C₁₋₆ alkyl group; each R³ represents H, aC₁₋₆ organic moiety, or a second RSiR¹ _(n) (OR²)_(3-n) group, which maybe the same as or different from the first such group; each R⁴represents a divalent organic moiety; =p1 and n is 0 or
 1. 3. The primerof claim 1 wherein the adhesion promoter is the reaction product of amultifunctional isocyanate and at least one organosilane containing anNCO-reacting hydrogen of the formula: ##STR13## or of the formula:

    HSRSiR.sup.1.sub.n (OR.sup.2).sub.3-n                      (IV)

or mixtures thereof, wherein:each R represents a divalent organicmoiety; each R¹ represents hydrogen or a C₁₋₄ alkyl group; each R²represents a C₁₋₆ alkyl group; each R³ represents H, a C₁₋₆ organicmoiety, or a second RSiR¹ _(n) (OR²)_(3-n) group, which may be the sameas or different from the first such group; and n is 0 or 1, and whereinthe equivalent ratio between the NCO groups of the multifunctionalisocyanate and the NCO-reacting hydrogens is at least about
 3. 4. Theprimer of claim 1 further comprising one or more additives selected fromthe group consisting of catalysts, moisture scavengers, NCO stabilizers,carbon black, non-black fillers, and defoaming agents.
 5. A method forpromoting the adhesion of an elastomeric adhesive to at least onenonporous substrate comprising treating the nonporous substrate with theprimer of claim
 1. 6. The method of claim 5 wherein the elastomericadhesive is adhered to two different substrates, and the same primer isapplied to both substrates.
 7. The method of claim 6 wherein theelastomeric adhesive is selected from the group consisting of urethanes,silylated urethanes, silyl-terminated polyethers and silicones.
 8. Theprimer of claim 3 wherein said organosilane is an amino-alkoxysilane inaccordance with Formula III.
 9. The primer of claim 3 wherein saidorganosilane is an amino-alkoxysilane in which R₃ is a C₁₋₆ organicmoiety.
 10. The primer of claim 9 wherein R₃ is phenyl.
 11. The primerof claim 10 wherein said amino-alkoxysilane isN-phenyl-gamma-aminopropyltrimethoxysilane.
 12. The primer of claim 3wherein said organosilane is a mercapto-alkoxysilane in accordance withFormula IV.
 13. The primer of claim 12 wherein saidmercapto-alkoxysilane is gamma-mercaptopropyltrimethoxysilane orgamma-mercaptopropylmethyldimethoxysilane.
 14. The primer of claim 1wherein said silane-modified polyester polymer is the reaction productof:a) the reaction product of a difunctional polyester polyol dissolvedin an anhydrous solvent with at least one difunctional isocyanate of theformula OCN--R⁴ --NCO; and b) at least one organosilane containing anNCO-reacting hydrogen of the formula: ##STR14## or of formula:

    HSRSiR.sup.1.sub.n (OR.sup.2).sub.3-n                      (IV)

or mixtures thereof, wherein:each R represents a divalent organicmoiety; each R¹ represents hydrogen or a C₁₋₄ alkyl group; each R²represents a C₁₋₆ alkyl group; each R³ represents H, a C₁₋₆ organicmoiety, or a second RSiR¹ _(n) (OR²)_(3-n) group, which may be the sameas or different from the first such group; each R⁴ represents a divalentorganic moiety; and n is 0 or
 1. 15. The primer of claim 14 wherein themolar ratio of difunctional isocyanate to difunctional polyester polyolis about two to one.
 16. The primer of claim 14 wherein the molar ratioof organosilane to the reaction product of a) is at least about two toone.